To obtain round trays for the baking of cakes such as angel food cakes, and the like, the tray is customarily made in two pieces, a round bottom and curved sides which are then glued together. That is, two separate blanks are processed, folded, and glued together.
When a single blank has been used, the sides have been upstanding from the bottom and folded upward about curved fold lines from the bottom, which typically caused the entire bottom to curl and not lie flat. Alternatively, when straight fold scores were used, the bottom had an undesired polygonal shape.
In upside-down cakes, such as angel food cakes, it is desirable to have the top of the cake substantially flat and to have the top also appear to be substantially rounded.